JP-2009-222009A shows an electrically-driven compressor provided with an inverter unit on its housing. The inverter unit is comprised of an inverter cover, a drive circuit, and a cooling plate. The inverter cover covers the drive circuit and the cooling plate. The cooling plate is arranged so that its outer surface confronts the housing. A switching element of the drive circuit is disposed on the cooling plate. A refrigerant passage is formed between a groove of the housing and the cooling plate.
The refrigerant flows in S-shaped refrigerant passage formed in the housing. Then, the refrigerant flows into the compressor and is compressed. The switching element, which generates heat, is cooled by the refrigerant flowing in the refrigerant passage through the cooling plate.
In a case of a battery charger, a plurality of switching elements is provided to the battery charger. Since the switching elements generate a lot of heat, it is necessary to cool the switching elements efficiently.